tgwhitley

I am building a Typhoon 909 inch version 1988 vintage I have one uncut cowl from Gator RC and would like to try my hand at making another. It appears to have been made in two pieces and joined after making halves. Can someone help me with a tutorial about making mold from exisiting part and save cowl for use after making mold? Also the part making process after mold is finished.



Thanks

Tim

ChiefK

Great topic.... I'll be anxiously waiting to learn how to do this too.
Any relation to Jim Whitley?

ChiefK

kitfox1

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Fibre Glast (www.fibreglast.com) in their web site, under learning center has a training video on how to make a mold for a cowl. Also, check youtube for other videos on how to make fiber glass molds.

lfinney

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the composites and fabrication forum has loads of example here on RCU

tgwhitley

ChiefK I am not related to Jim Whitley have meet him on more than one occasion very nice fellow. I searched briefily the C&F forum and found no threads using the original part to make mold by again my search abilities may be to limited. I would like to pull mold from original part I have without damage to the cowl. Any suggestions would be wonderful.

Thanks

Tim

Leohenriques

R_G

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That is an excellent series of videos! Very informative!

RG

MTK

Tim,

Responders are correct, there is a ton of info out there, some of which I have written. A very quick intro to the subject follows:

1- Let's assume you want to make a simple cavity mold of the canopy. That's different and a lot less work than a 2 piece clamshell mold that would be necessary if the original was flanged
2- Determine how you will fixture the original part you wish to mold. I have used pressed paperboard successfully, from local Home Depot, the type that has one shiny surface. Plexiglas sheet, glass, waxed or parchment paper, many different things can be used as a base for fixturing
3- Fix the original part onto the base. I use simple Plumber's putty rolled into beads. I surround the base and press into the original part's lip to seal. Then I cut carefully around the base with an exacto leaving a sharp corner.
4- Wax carefully, part and base, paying attention to the corners. I use PartAll release and have found it to work very well for most molding. I wax at least 3 coats and gently polish between coats. For flimsy canopies, waxing can be done first and then the part can be fixtured onto the base with only minor waxing required
5- I spray one very light tack coat of PVA and let it flash for a couple minutes and then come back with one light-medium coat. As the PVA dries, it becomes shiny. Must be dry completely, at least an hour
6- I use epoxy for the actual mold. CJ Composites or US composites has some pretty good epoxy that is inexpensive. I mix about 50 grams at a time per instructions and add about a gram of carbon powder to the epoxy. Then I add enough fumed silica to form a thin gel.
7- Brush the base coat onto the plug paying close attention to the corners. These must be fully filled for sharp edges. You want a fairly thick coat of about 1/16"-3/32" everwhere. Gently heat the work with a monokote heat gun to get rid of any air bubbles. Let the first coat kick to where it is set but still tacky. This first coat is critical. Must get it into all corners and make sure it is smooth. It will be the surface of your mold afterall
8- Mix another batch of base coat same as the first, and cover any thin spots. Let it kick off.
9- I use 6oz cloth, two layers, bias cut (cut on 45 degree angle). I use the same epoxy mix to wet it out except no fillers; epoxy only
10- Then 9-10 oz cloth, 2 layers minimum are added, orthogonal orientation of fibers. The bias orientation and the orthogonal orientation settle the mold down. You want about 30 to 40 oz equivalent of cloth minimum (2 layers 6 oz and 2 layers of 10 oz is 32 ozs)
11- For simple cavity molds I usually add a plywood skirt all around the mold to further stabilize it.

12- LET IT CURE for 48 hours. Leave it alone, don't disturb it. Once cured, lightly tap the glass with a piece of heater hose or garden hose to separate from the original

To prepare for layup, wax using Part All 3-5 coats, polishing between coats. If you want to prime or paint in the mold, make sure you use PVA after waxing. For smaller canopies like the Typhoon's, I'd use 3 oz cloth, one layer. Make sure you cure the part completely before attempting to pop it off the mold

There are other methods with plaster as the backing reinforcement. I've found the method I described to be repeatable and produce a very good mold